JPS61206639A - Laminated sheet for molding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a laminated paper for forming, and more specifically,
This invention relates to laminated paper that does not bulge between layers during molding and cooking.

(Prior Art) In recent years, with the spread of microwave ovens and various open-air ovens, frozen foods are rapidly becoming popular as foods that can be easily heated and baked. Particularly recently, in cafeterias and mobile food sales in places where large numbers of people gather, such as various exhibitions, trade fairs, deharts, amusement parks, cars, etc., hygienic, warm, and aesthetically pleasing food can be quickly and indispensable. There is a need for food that can be provided in large quantities according to the demand, and this requires commercial freezing and
Cooked foods are suitable. Specifically, gratin, torian, pizza pie, bakery, curry rice, unaju, sukiyaki, etc. are filled in heat-resistant paper containers, i.e., ovenable paperboard trays, frozen, and stored as needed. It is thawed and cooked before being provided to users.

Paper containers not only have excellent storage and transportation properties, but they also have heat resistance that allows them to be used in microwave ovens, open cooking equipment, etc. It is a highly practical container that is portable, has excellent shape retention, and has no particular safety problems.Furthermore, it can be easily incinerated after use.

Conventional paper containers are generally made of laminated paper with a thermoplastic resin layer on one side of a highly sized base paper, which is then molded so that the food is in contact with the thermoplastic resin layer. .

(Problems to be Solved by the Invention) When preparing frozen foods for commercial purposes, from the viewpoint of cooking time and cost, after thawing using the live steam blowing method, the food is heated in a large microwave oven or in a large open oven, etc. Although there are many
During thawing, it is kept humidified and heated for a considerable period of time. Therefore, when conventional paper containers such as those mentioned above are used, moisture is sucked in from the base paper side, the paper container is greatly deformed, and the Vi lid may come off in some cases, making it impossible to close the lid again. Ta.

Furthermore, even if the problem of deformation of the paper container does not occur, there is still water absorbed by the base paper, which has the disadvantage of requiring unnecessary energy and time when cooking after thawing. was.

(Means for Solving the Problems) In order to solve the above-mentioned drawbacks, the present inventors have developed a molded container for filling food using laminated paper in which #A town plastic resin layers are provided on both sides of the base paper. However, when the thermoplastic resin and the mold of the thermoforming machine are pressed together at high temperatures during thermoforming, the resin layer softens and melts and adheres, resulting in poor mold release and problems during thermoforming. It has been found that even if water in the base paper expands due to heating during cooking or cooking, there is no place for it to escape, resulting in peeling between the thermoplastic resin layer and the base paper, resulting in defects such as blistering. The above mold release failure could not be sufficiently improved even when the mold surface was treated with silicone resin or Teflon.

The inventors of the present invention have conducted intensive studies to simultaneously solve the various problems mentioned above, such as deformation of the base paper due to moisture absorption, poor mold release during molding, and blistering during heating, and have developed the present invention. reached.

That is, the laminated paper for molding of the present invention has thermoplastic resin layers on both sides of a base paper that has an inorganic pigment coating layer on one side, and further has thermoplastic resin layers on the surface of the side that does not have the inorganic pigment coating layer. It is characterized by having an upper paper layer. The base paper used in the present invention is a single-layer or multi-layer (combined paper, etc.) paper made using pulp, and the basis weight is usually 10
o i/, , (~5001)/, , (are used).

After controlling the absolute dry moisture content of the base paper layer to 6 to 8%, thermoplastic resin layers are provided on both sides. If it exceeds 8%, the molded laminated paper tends to blister when heated, and if it is less than 6%, the molded special base paper lacks elasticity, resulting in paper breakage, poor ruled lines, etc. Further, the inorganic pigment coating layer on the base paper is composed of a coating composition containing an inorganic pigment and an organic binder as components, and the coating width is preferably 1 to 40 mm, more preferably 15 to 20 mm.

As the inorganic pigment used in the coating layer, white pigments such as methane oxide, aluminum hydroxide, and clay are usually used alone or in combination, but other colored pigments can also be used if desired.

Further, the organic binder used in the coating layer is not particularly limited, but it is preferable to appropriately select and use one that has excellent adhesiveness to the thermoplastic resin layer laminated to the coating layer.

In addition, the thermoplastic resins provided on both sides of the base paper coated with inorganic pigments include polyolefin resins such as polypropylene resin, polyethylene resin, and polymethylpentene resin, thermoplastic polyester resins such as polyethylene terephthalate and polyethylene terephthalate, and others. Plastics with good film-forming properties are used, but polyolefin resins are preferably used especially when heat resistance and low cost substantially convexity are desired.

These resins may be directly laminated on both sides of a base paper provided with an inorganic pigment coating layer by extrusion coating, or
A film formed in advance may be laminated.

Alternatively, a resin layer may be provided on the front surface after performing so-called sandwich lamination in which a resin is poured between the back surface of the base paper and the upper paper.

The thickness of these resin layers is 20 to 100 mm on the front and back sides, respectively.
μ is preferable, and about 20 to 40 μ is particularly suitable. 2
If it is less than 0μ, the water resistance, oil resistance, acid resistance, salt resistance, and surface properties are insufficient, and if it is more than 100μ, the characteristics of the synthetic resin will be excessively exhibited, and the effectiveness as a paper container will be diminished.
It is also economically disadvantageous.

The glazing paper to be pasted on the back side is preferably kraft paper with a basis weight of 60 to 70. From the viewpoint of aesthetics, bleached kraft paper or a desired colored kraft paper with fine printing is suitable. .

If you use high-quality paper, pure white roll, or thin paper instead of kraft paper, the strength of the paper will be weak and the stretchability will be poor, so paper will break at some corners of trays, etc., which are molded products, and at the 7-lung folded part, which is undesirable. Also, even kraft paper costs 30~
The same applies to the following thin sheets; if the thickness is 70'/.1 or more, the heat conduction during molding is insufficient, and the paper layer is too thick, resulting in insufficient moldability.

The method for providing the veneer on the thermoplastic resin layer is not particularly limited, but as described above, so-called sandwich lamination is practical.

The laminated paper for molding obtained as described above can be thermoformed so that the side of the base paper with the inorganic pigment coating layer is on the inside, and can be used as a container used for filling foods and the like.

(Function) The laminated paper for molding of the present invention having the structure of thermoplastic resin layer (surface) obtained as described above/no inorganic pigment coating/base paper/thermoplastic resin layer/upper paper layer (back side) can be used to make containers by thermoforming, but the thermoforming conditions are usually 30-70°C for the male mold and 100-100°C for the female mold.
Since it is carried out at 70°C, there is no adhesion problem with the thermoplastic resin layer on the surface on the male mold side, which is relatively low at 30 to 70°C, and since the back side that is in contact with the high temperature female mold is the upper paper layer, No adhesion problems even at high temperatures. Also, when the laminated paper is heated, the slight amount of moisture present in the base paper expands, but the inorganic pigment (coating layer) exists between the thermoplastic resin layer on the surface and blocks moisture. , no blistering (peeling) occurs in the thermoplastic resin layer. In addition, the problem of peeling between the base paper and the thermoplastic resin layer on the back side does not occur as a result of blistering because it is supported by the outermost layer of upper paper.

Furthermore, since the base paper does not absorb moisture, containers made using this laminated paper do not lose their shape;
If you attach a lid to this, the lid will not come off during cooking,
Furthermore, it is easy to reattach after being removed.

(Example) The present invention will be described in more detail below using Examples, but the present invention is not limited thereto.

Example-1 Multilayer paper with a sizing degree of 1200 seconds and a basis weight of 370'/y was coated with a coating composition 18'/, z consisting of styrene-butadiene latex, an organic binder of casein, and clay-calcium suboxide. Absolute moisture content 5.2% in advance,
The humidity was adjusted to 7.2%, 81% and 9.9% and stored.

Next, a flower pattern was printed on each of the above base papers using the T-gui method, and OP varnish was applied. A polypropylene resin was extruded between the bleached kraft paper (upper paper) and a sandwich laminate was applied. The thickness of the resin is 3
It was 3μ. The one in which the top paper is laminated on the coated layer side of the base paper is called the front sandwich, and the one laminated on the non-coated side is called the back sandwich.Furthermore, polypropylene resin is extruded and laminated to a thickness of 63μ on the opposite side of the sandwich laminate. Samples A1 to 6 shown in Table 1 consisting of front sand or back sand
A laminated paper was obtained.

FIG. 1 shows a cross-sectional view of the laminated paper (back sand) of the present invention, where 1 is the base paper, 2 is the inorganic pigment coating layer, 3 is the thermoplastic resin layer, and 4 is the top paper.

A tray-shaped molded container is made from the samples of 1 to 2.
A heating blistering test was conducted on an empty container for 5 minutes at the temperature listed in the table.

In addition, water 2501 was poured into each tray obtained by separate molding, the switch was set to high, a water boiling test was conducted for 10 minutes, and the shape of the container was observed.

Furthermore, the flame of a gas lighter was directly applied to the front and back surfaces of samples 41 to 6, and the state of blisters before combustion was observed.

In addition, in order to confirm the moldability, containers were molded using a paper tray molding machine manufactured by Geitg, and the moldability at that time is shown in Table 1.

Example-2 Using the same base paper (absolute moisture content -7.2%) and top paper as in Example-1 Sample/I64, the laminating resin was changed to low-density polyethylene, and a back-sand laminated paper was obtained. - The resin thickness was 30μ in all cases.

Table 1 shows the results obtained by the same test method as in Example-1.

From the above results, it can be concluded that ■ When the absolute dry moisture content of the base paper exceeds 8%, the occurrence of blistering in the tray increases significantly. (1) If the absolute dry moisture content of the base paper is less than 6%, molding defects such as paper cuts and edge cuts will occur frequently in the tray. (2) Even in the case of polyethylene resin, the heating temperature is 140℃. It is clear that blistering does not occur at temperatures below .degree. C. and that it can be used satisfactorily at relatively low temperatures, indicating that the laminated paper of the present invention is extremely excellent.

Comparative Examples 1, 2, 3 Using the same base paper (absolute moisture content -7.2%) and the same resin as in Example 1, the upper paper to be laminated was thin paper (to 27), high-quality paper ( 53~) A backside laminated paper and a laminated paper without a top paper were obtained.

The thickness of each resin was 30μ.

We conducted a molding test on these samples using an actual machine, observed the mold releasability from the female mold, and observed paper breakage defects at some corners of the molding tray, and compared the results with the Example 1/164 sample. It is shown in Table-2.

From this result, it is clear that the release effect is extremely excellent when the top paper is laminated, and that bleached kraft paper is good for the lamination top paper.

Table 2 (Note) 0 Mold release property: Tray release property from the female mold heated to 138°C 0 Paper cut Nidori Outer corner Some paper breakage defects 0 Laminated paper composition: Back sand (effect of the invention) As described above, the laminated paper of the present invention has good moldability and does not bulge when heated, and the containers obtained by molding it hardly deform during cooking, making it highly practical. be.

[Brief explanation of drawings]

The figure represents a cross-sectional view showing the layer structure of the laminated paper for molding of the present invention. 1...Base paper 2...Inorganic pigment coating layer 6...Thermoplastic resin layer 4...Top paper Patent applicant Kojin Co., Ltd. (and 1 other person)

Claims (3)

[Claims] (1) Thermoplastic resin layers are provided on both sides of the base paper, which has an inorganic pigment coating layer on one side, and an upper paper is attached to the surface of the thermoplastic resin layer on the side that does not have the inorganic pigment coating layer. A laminated paper for molding that is characterized by being laminated. (2) The laminated paper for molding according to claim 1, wherein the top paper is bleached kraft paper. (3) The laminated paper for molding according to claim 1, wherein the base paper has an absolute dry moisture content of 6 to 8%.